The present invention relates generally to welding methods and apparatus, and more particularly to a drawn arc welding method and a drawn-arc-weld ferrule.
Conventional methods for attaching first and second parts together, such as a steel attachment ring and a steel rod of a vehicle shock absorber, include welding such as drawn arc welding. In one conventional drawn arc welding technique, the attachment ring is connected to a grounded drawn-arc-weld electrode, and the rod is connected to a positive drawn-arc-weld electrode. A tenon on the rod is brought in contact with the ring and is then withdrawn to create a welding arc which melts portions of the rod and the ring creating a weld puddle which leads to the welding together of the parts. A conventional ceramic ferrule is used to contain the weld puddle when the diameter of the tenon is larger than about six to eight millimeters or when a weldment dimension is larger than about ten millimeters when drawn arc welding is performed with or without one or both of the parts having a tenon. Conventional grooves in the ceramic ferrule allow gases created during welding to escape. Ceramic drawn arc weld ferrules are designed not to melt during welding.
After the weld is made, a conventional one-piece ceramic drawn-arc weld ferrule is broken up to be removed from the welded parts, and the broken ferrule pieces are then discarded. Conventional ceramic drawn-arc-weld ferrules are known which have been split in half creating two separate segments, wherein each segment is mounted to a ferrule holder. The ferrule holders are moved toward each other to bring the segments together to create the ferrule for surrounding the weld zone for drawn arc welding. The ferrule holders are moved away from each other after the parts have been welded together allowing removal of the welded parts from the welding machine. Such two-piece ceramic drawn-arc-weld ferrules are reusable for only a few hundred welds and are very expensive to machine or sinter to the necessary shapes. Conventional ferrule holders are known which contain passages for directing gases (such as a mixture of argon and carbon dioxide) to shield the weld zone and stabilize the welding arc.
What is needed is an improved drawn arc welding method and an improved drawn-arc-weld ferrule.
A first method of the invention is for attaching first and second parts together and includes steps a) through e). Step a) includes positioning the first and second parts for drawn arc welding the first and second parts together. Step b) includes obtaining a drawn-arc-weld ferrule comprising metal. The terminology xe2x80x9ccomprising metalxe2x80x9d includes comprising a metal or comprising a plurality of metals. Step c) includes positioning the drawn-arc-weld ferrule for use in drawn-arc-welding together the positioned first and second parts. Step d) includes cooling the drawn-arc-weld ferrule. Step e) includes drawn arc welding the positioned first and second parts together using the positioned drawn-arc-weld ferrule.
A second method of the invention is for attaching first and second parts together and includes steps a) through e). Step a) includes positioning the first and second parts for drawn arc welding the first and second parts together. Step b) includes obtaining a drawn-arc-weld ferrule including separate segments each consisting essentially of metal or metal alloy or both, and each having a melting point lower than a maximum welding temperature reached during drawn arc welding together of the first and second parts. Step c) includes positioning together the segments to create a ferrule shape for use in drawn-arc-welding together the disposed first and second parts. Step d) includes cooling each of the segments. Step e) includes drawn arc welding the positioned first and second parts together using the positioned segments.
A first expression of an embodiment of the invention is for a drawn-arc-weld ferrule which includes metal.
A second expression of an embodiment of the invention is for a drawn-arc-weld ferrule including separate segments each including metal.
Several benefits and advantages are derived from one or more of the methods of the invention and/or from one or more of the expressions of an embodiment of the invention. Use of a drawn-arc-weld ferrule including metal, such as a copper ferrule, provides a drawn-arc-weld ferrule which is inexpensive to machine to the necessary shapes. In one example, cooling the ferrule will prevent the ferrule from melting from the heat generated by drawn arc welding and should allow the ferrule to be reused for several thousand times to drawn arc weld together parts such as steel attachment rings and steel rods of vehicle shock absorbers.